The present invention relates to open reel type tape recorders. More particularly, the invention relates to a pinch roller drive mechanism and a control circuit therefor in an open reel type recorder utilizing a dual capstan system.
Recently, a tape recorder employing a so-called "dual capstan system" has been developed and is commercially available in which two capstans are disposed respectively upstream and downstream of the recording, reproducing (playback) and erasing heads with two pinch rollers one of which is disposed to abut with each of the two capstans.
However, a tape recorder of this type is disadvantageous in that all of the magnetic heads, namely, the recording, reproducng and erasing heads are disposed between the two capstans and accordingly the magnetic heads cannot be sufficiently spaced from one another. Specifically, the erasing head should be sufficiently spaced from the recording head because the magnetic flux of the erasing head adversely affects the recording head. That is, it is desirable that the distance between the capstans be increased. However, it is not practical to increase the distance because if the distance is increased, the drive system unavoidably becomes bulky and the reels are liable to rotate irregularly because of elongation of the belt.
This difficulty may be eliminated by positioning the erasing head outside of the capstans rather than between the capstans. However, in this case, it is difficult to satisfactorily bring the magnetic tape into sliding contact with the erasing head and accordingly the position of the tape with respect to the erasing head tends to vary greatly as result of which the material recorded on the tape may be irregularly erased or the material recorded on channels other than that which it is desired to erase may be erased.
Furthermore, a conventional tape recorder is intricate in construction because it is necessary to shift the pinch rollers to three different positions, namely, a recording position, a pause position and a stop position.